diff --git a/api/services/mps_service_key_client.py b/api/services/mps_service_key_client.py
index 6c478d1..2c7fc56 100644
--- a/api/services/mps_service_key_client.py
+++ b/api/services/mps_service_key_client.py
@@ -263,10 +263,12 @@ class MPSServiceKeyClient:
             HTTPException: If the API call fails
         """
         async with httpx.AsyncClient(timeout=self.timeout) as client:
-            response = await client.post(
-                f"{self.base_url}/api/v1/service-keys/usage",
-                json={"service_key": service_key},
-                headers=self._get_headers(organization_id, created_by),
+            response = await client.get(
+                f"{self.base_url}/api/v1/service-keys/usage/self",
+                headers={
+                    "Authorization": f"Bearer {service_key}",
+                    "Content-Type": "application/json",
+                },
             )
 
             if response.status_code == 200:
@@ -429,10 +431,12 @@ class MPSServiceKeyClient:
         """
         try:
             with httpx.Client(timeout=self.timeout) as client:
-                response = client.post(
-                    f"{self.base_url}/api/v1/service-keys/usage",
-                    json={"service_key": service_key},
-                    headers=self._get_headers(organization_id, created_by),
+                response = client.get(
+                    f"{self.base_url}/api/v1/service-keys/usage/self",
+                    headers={
+                        "Authorization": f"Bearer {service_key}",
+                        "Content-Type": "application/json",
+                    },
                 )
                 return response.status_code == 200
         except Exception:
diff --git a/api/tests/test_mps_service_key_client.py b/api/tests/test_mps_service_key_client.py
new file mode 100644
index 0000000..9cd629e
--- /dev/null
+++ b/api/tests/test_mps_service_key_client.py
@@ -0,0 +1,89 @@
+import pytest
+
+from api.services.mps_service_key_client import MPSServiceKeyClient
+
+
+class _Response:
+    def __init__(self, status_code: int, payload: dict | None = None, text: str = ""):
+        self.status_code = status_code
+        self._payload = payload or {}
+        self.text = text
+        self.request = object()
+
+    def json(self):
+        return self._payload
+
+
+def test_validate_service_key_uses_bearer_self_usage(monkeypatch):
+    calls = []
+
+    class FakeClient:
+        def __init__(self, timeout):
+            self.timeout = timeout
+
+        def __enter__(self):
+            return self
+
+        def __exit__(self, exc_type, exc, tb):
+            return None
+
+        def get(self, url, headers):
+            calls.append(("GET", url, headers))
+            return _Response(200)
+
+    monkeypatch.setattr("api.services.mps_service_key_client.httpx.Client", FakeClient)
+
+    client = MPSServiceKeyClient()
+
+    assert client.validate_service_key("mps_sk_paid") is True
+    assert calls == [
+        (
+            "GET",
+            f"{client.base_url}/api/v1/service-keys/usage/self",
+            {
+                "Authorization": "Bearer mps_sk_paid",
+                "Content-Type": "application/json",
+            },
+        )
+    ]
+
+
+@pytest.mark.asyncio
+async def test_check_service_key_usage_uses_bearer_self_usage(monkeypatch):
+    calls = []
+
+    class FakeAsyncClient:
+        def __init__(self, timeout):
+            self.timeout = timeout
+
+        async def __aenter__(self):
+            return self
+
+        async def __aexit__(self, exc_type, exc, tb):
+            return None
+
+        async def get(self, url, headers):
+            calls.append(("GET", url, headers))
+            return _Response(
+                200,
+                {"total_credits_used": 12.5, "remaining_credits": 87.5},
+            )
+
+    monkeypatch.setattr(
+        "api.services.mps_service_key_client.httpx.AsyncClient", FakeAsyncClient
+    )
+
+    client = MPSServiceKeyClient()
+
+    assert await client.check_service_key_usage("mps_sk_paid") == {
+        "total_credits_used": 12.5,
+        "remaining_credits": 87.5,
+    }
+    assert calls[0] == (
+        "GET",
+        f"{client.base_url}/api/v1/service-keys/usage/self",
+        {
+            "Authorization": "Bearer mps_sk_paid",
+            "Content-Type": "application/json",
+        },
+    )